Effects of stress and genomic plasticity on the reproductive mode of facultative apomictic plants of weeping lovegrass [Eragrostis curvula (Schrad.) Nees].

RODRIGO J. M; OCHOGAVIA A.; MEIER M.; ZAPPACOSTA D.; PESSINO S.; ECHENIQUE V.

Buenos Aires

Simposio; The 6ht International Symposium on the Molecular Breeding of Forage and Turf.; 2010

To  overcome  an  environmental  stress,  plants mostly  develop  physiological  responses  triggered by genetic or epigenetic  changes, some of them involving  DNA methylation  and  transposon  activation.  It  has  been  proposed  that  apomixis  control  occurs  by  temporal  or  spatial  deregulation  of  a  sexual  process.  In  this  sense,  apomixis  will  be  express depending on genetic and epigenetic factors  affected by the environment. The  aim of this study was to analyze the genetic and epigenetic changes that took place in a  weeping  lovegrass  tetraploid  plant  (UNST1131)  obtained  by  chromosome  doubling  which showed a high level of sexual reproduction when it was generated (2003) and 15- 20% four  years later (2007). The genetic (AFLPs) and epigenetic (MSAPs) profiles of  this  plant  obtained  by  colchicine  treatment  from  a  sexual  diploid  plant  obtained  by  tissue  culture  were  analysed.  These  profiles  were  compared  with  the  corresponding  patterns of the apomictic tetraploid plant (cv. “Tanganyika”), the origen of this euploid  series. Gene libraries (cDNA, 2003) from both plants were screened for retrotransposon  activity.  On  the other hand, a  progeny test of somaclones from cv.  “Tanganyika” was  performed using isozymes (1998) and RAPDs (2007). AFLP patterns (UNST1131 and  cv. Tanganyika) showed variation between 2003-2007, indicating genetic changes over  time  and  certain  genome  plasticity.  Also,  MSAP  results  showed  that  plants  were  epigenetically  more  similar  to  each  other  in  2007  than  at  the  begging  of  the  tetraploidization,  with  a tendency  to  methylation over demethylation. Retrotransposon  activity  was  higher  in  UNST1131,  which  could  be  explained  as  a  response  to  tissue  culture and/or polyploidization stress. Progeny test of somaclones using isozymes and  RAPDs  indicated  a  high  level  of sexual  reproduction  (variable  progeny)  immediately  after the tissue culture procedure (1998) and a high level of uniform progeny (apomixis)  ten years later. Taken together these results would indicate that epigenetic mechanisms  affected  by  genomic  stresses  could  be  regulating  the  expression  of  apomixis  in  this  grass.